JPH0720481B2 - Absorption structure for absorbing body fluids - Google Patents

Description

TECHNICAL FIELD The present invention relates to an absorbent structure used for a disposable diaper or the like.

(Prior Art) Generally, in a disposable diaper, a liquid-permeable liner is located on the innermost side closest to the wearer's skin, and a liquid-impermeable cover is located on the outermost side of the diaper farthest from the wearer.
Then, between the liner and the cover, there is a bat which is a liquid absorbent fiber material.

Generally, the most economical liquid absorbent material for use in disposable diapers is a cellulosic fiber, such as ground wood pulp, commonly known in the art as "fluff pulp" or simply "fluff." Bats made of such fibers have low density and high liquid absorption capacity, but very low wicking capacity. Therefore, the central part of the inseam located below the worn diaper tends to get very wet when body fluids are excreted, while the upper part of the diaper (when worn) has a high tendency to get wet. The included fluff remains dry without its absorbent capacity being used.

This raises some issues. First of all
Secondly, fluffing a diaper is uneconomical because most of it is wasted and wasted. Next, wetting may occur from the central portion of the diaper soaked with the liquid. Further, such concentration of the liquid on a part of the diaper makes the diaper wearer feel uncomfortable.

To avoid some of these problems, US Pat.
The conventional solution described in the specification of 213,459 is
The size of the stomata is reduced so that the capillary action of the stomata is sufficient to overcome gravity and move excretory liquid upward in the diaper. However, it has been conventionally noted that reducing the average pore size leads to a reduction in the total absorbable amount. Nevertheless, in order to disperse the liquid better over the area available for the absorption of liquid in the diaper, this solution offers a method which is generally chosen in the past, despite the loss of liquid absorbable capacity. is there.

Another method for solving such a problem is adopted in US Pat. No. 4,213,459. That is, a local portion composed of high-density fluff is provided in the bat so that the excreted liquid is sucked up to a higher position of the diaper. While this method is technically advanced, it is not without its drawbacks. First of all, the diaper surface directly below the lining closest to the wearer's skin becomes drenched. Further, the only place liquid can move from the low density material to the high density material is at the boundary where the low density material is adjacent to the high density material. Thus, the above patents state that the area around the high density area of the bat should remain undensified.

In Japanese Examined Patent Publication No. 56-85401, a liquid absorbent layer is composed of a first absorbent pad on the human body side and a second absorbent pad on the outer side, and the second absorbent pad is denser than the first absorbent pad and has an average fiber content. An absorbent article is disclosed in which the spacing is smaller than the average fiber spacing of the first absorbent pad. The purpose of this configuration is to absorb the human body effluent that has reached the first absorbent pad into the second absorbent pad and quickly send it to a distant position within the second absorbent pad.

Japanese Patent Laid-Open No. 57-10334 discloses an absorbent article in which a first absorbent layer and a second absorbent layer are formed, the first absorbent layer is formed to be lightweight, and the second absorbent layer contains a superabsorbent polymer. Is disclosed. The aim of this absorbent article is also to quickly transfer the liquid that has reached the first absorbent layer to the second absorbent layer and hold it in the second absorbent layer.

(Problems to be Solved by the Invention) The structures disclosed in JP-B-56-85401 and JP-A-57-10334 both rapidly transfer liquid from the first absorption layer to the second absorption layer. And avoid touching the human body. However, this configuration has a drawback that most of the absorbent capacity of the absorbent material of the first absorbent layer is wasted without being used, and the absorbent material is wasted.

The present invention is obtained by paying attention to such a point, and is a disposable that can greatly utilize the absorbing ability of the absorbent used and that can suppress contact of the liquid from the human body with the body as much as possible. The challenge is to provide clothing.

(Means for Solving the Problem) In order to solve this problem, the disposable garment according to the present invention has an absorbent pad, that is, a pad, having at least two layers of cellulosic fibers having different densities or average pore diameters. ing. In a disposable diaper having a liquid-permeable liner facing the human body, an outer liquid-impermeable cover, and a liquid-absorbing material between them, the absorbent material provided by the present invention comprises a first density or A first layer of cellulosic fibers having a pore size of 1 is disposed under the permeable lining and a second layer of cellulosic fibers having a higher density or a smaller average pore size than the first layer. The layer is formed as a layer different from the first layer, and the second layer is located at least below the portion where the first layer is formed.

A feature of the present invention is that the average pore size of the second layer, that is, the second average pore size is smaller than the average pore size of the first layer, that is, the first average pore size, and the distribution of the pore size of the first layer is The distribution of the pore size of the second layer overlaps, and the maximum pore size of the second layer is larger than the minimum pore size of the first layer.

(Operation) According to the present invention, since the average pore size of the second layer is smaller than the average pore size of the first layer, the liquid reaching the first layer is quickly absorbed by the second layer, It extends circumferentially along the second layer. Then, since the pore size distribution of the first layer and the pore size distribution of the second layer overlap, the maximum pore size of the second layer is larger than the minimum pore size of the first layer. The liquid spread along the two layers becomes at least partly returned to the first layer at a position away from the target area where the liquid first reaches the first layer. For this reason, in the present invention, the absorbent capacity of the first layer is utilized to a greater extent than in conventional absorbent articles.

The objects and advantages of the present invention can be fully understood with reference to the following detailed description read in conjunction with the drawings.

EXAMPLES Referring to the drawings, a disposable diaper 1 embodying the present invention generally comprises a liquid permeable liner 2 facing the human body,
It has a liquid impermeable cover 3 on the outside and a liquid absorbing material generally designated by 4 between them. The liquid absorbent material 4 has a first low density layer 5 of cellulosic fibers, such as ground wood pulp (fluff), which layer underlies the inner liner 2. The second high-density layer 6 made of fluff is located at least under the portion of the first low-density layer 5 so that excreted liquid can move from the low-density layer 5 to the high-density layer 6. Therefore, the lower surface 15 of the low density layer 5 should contact at least a portion of the upper surface of the high density layer 6. However, placing a layer of tissue paper between these layers 5, 6 does not depart from the scope of the invention.

Fluff, which is mostly softwood pulp, can be used for both layers 5,6. Alternatively, a layer of fluff that is mostly softwood pulp can be used for layer 5 and a layer of fluff that is a majority of hardwood for layer 6, in which case, as will be briefly described below. , Between the layers 5 and 6 the average pore size and, although not necessarily the density, vary. As used herein, the term "predominantly" means at least about 80%, and "predominantly" (pr
The word eponderantly) means at least about 50%.

In a first preferred embodiment shown in FIGS. 1 and 2,
The high-density layer 6 has a strip-like shape and extends from a target portion 7 where excreted liquid is first collected to a rear upper edge 8 of the diaper. By the high-density layer 6, the excreted liquid is sucked upward from the target portion 7 of the low-density layer 5 toward the rear edge 8 of the diaper 1. Furthermore, along the top region 18 of the dense layer 6 towards the top edge 8, surprisingly, there is substantially a fluid transfer back from the dense layer 6 to the low density layer 5.
This backflow occurs from the high-density layer 6 toward the low-density layer 5, but the fluid sucked by the low-density layer 5 is sufficient to satisfy the unsaturated capillary force close to that of the high-density layer 6. In this case, the minimum pores of the low-density layer 5 are the same as those of the high-density layer 6 so that the pore diameters of both layers partially match.
It is smaller than the maximum pore of. Although the liquid is discharged from the high-density layer 6 by the low-density layer 5, the low-density layer 5 does not become soaked, the wearer's comfort is maintained, and the low-density layer 5 has It has the advantage that most of the absorption capacity is utilized.

3 to 5 show another embodiment according to this aspect of the present invention. In the second preferred embodiment of FIGS. 3 and 4, the dense layer 6 is strip-shaped and extends the entire length of the diaper. In the third preferred embodiment shown in FIG. 5, the high density layer 6 is coextensive with the low density layer 5.

Still another modification of the above-described embodiments is one in which the pore diameter is changed without necessarily changing the density. As an example, instead of the layer 6 of high-density softwood fluff fiber, at least about 50%, preferably about 80% to 10% of softwood fluff fiber having a density approximately the same as the layer 5 of low-density softwood fluff fiber.
The present inventors have found that by using 0%, it is possible to utilize hard wood fluff having a fine fiber size. The reason why this can be done is that the pore diameter of the hardwood fluff is smaller than the pore diameter of the softwood fluff material. As a result, when hardwood fluff fibers are used instead of high density softwood fluff fibers, two different pore size distributions are still obtained even though the densities of both layers are the same. This configuration does not depart from the scope of the present invention. So, for example, "mostly"
The upper layer 5 obtained by being a softwood fluff pulp
Of two fluff fractions having a large pore size structure and a micropore structure of the lower layer 6 consisting of a "majority" hardwood fluff pulp, having a certain density (preferably around 0.1 g) throughout. Compressed to / cm ³ ) produces similar results to the examples described above and can be used satisfactorily.

The second embodiment of the present invention is provided with a portion of super absorbent material (SAM) 9 as the liquid absorbent material 4. The term "superabsorbent material" is used herein to refer to one or more hydrocolloid materials capable of absorbing many times their own weight of water or aqueous fluids. These materials are generally produced by polymerizing one or more monomers, but when homopolymerized by conventional methods they become water-soluble polymers.
To render them water-insoluble and suitable for the present invention, these polymers or polymer mixtures are typically reacted (crosslinking agents are often used in this reaction) to form crosslinked polymers. Formed, thereby making it water-insoluble and swellable in water and hydrous fluids. Pseudo-crosslinking can also be formed by chain entanglement of high molecular weight polymers, which results in water insolubility (see, eg, US Pat. No. 4,340,706). Typically, these hydrocolloids are polyacrylic acid and its modified salts, such as methacrylic acid. Those commercially available products include WATER LOCK J-500 (trade name, manufactured by Grain Processing), ABASORB720 (trade name, Arakawa Chemical (USA).
And Aqualic-CA (trade name, manufactured by Mitsui).
Other superabsorbents also include those in which starch or cellulose is the main chain and crosslinked carboxylated cellulose is grafted with a hydrophilic polymer.

FIGS. 6 and 7 show a fourth preferred embodiment in which the superabsorbent material 9 is sandwiched by a first high density part 10 and a second high density part 11. These first and second high density portions 10 and 11 are arranged at the same place as the high density layer 6 in the above-mentioned three embodiments. However, it is generally preferred to position the superabsorbent material 9 in a region 17 slightly above the intermediate position between the target portion 7 and the top edge 8. As a result, another reservoir of the excreted liquid sucked up by the high density layer 6 is formed by the super absorbent material 9.

An important advantage of such a form of the present invention is that it promotes dispersion of the fluid along the length of the superabsorbent material.
In general, the superabsorbent 9 located in the fiber matrix improves the fluid distribution in the thickness direction of the liquid absorbent material 4. However, the swelling properties of the superabsorbent material 9 considerably impede the planar wicking action in the fiber matrix which supports this superabsorbent material 9. According to such an aspect of the invention, the wicking action along the entire length of the superabsorbent material 9 causes the superabsorbent material 9 to be distributed in the first high density part 10 and the second high density part 11. It occurs by sandwiching. As a result, the excreted liquid comes into contact with the upper and lower surfaces 12, 13 of the superabsorbent material 9 rather than the lower end 14. This is an improvement, as in the first aspect of the invention described with reference to FIGS. 1-5, against the movement of excretory fluid from one boundary to another, such as low density layer 5 and high density layer. An improvement of surface-to-surface contact between 6 is realized.

8 and 9 show another embodiment, in which superabsorbent material 9 is placed adjacent to an outer liquid impermeable cover and further covered with a single dense layer 6. On the other hand, the high density layer 6 is covered with the low density layer 5.

Here, (in FIGS. 8 and 9) layer 5 is softwood fluff pulp, layer 6 is hardwood fluff pulp (in FIGS. 6 and 7, layer 10 is softwood fluff pulp, layer 11 is hardwood fluff pulp). ) was used to full thickness of about 0.1 g / cm ³ having a uniform density and without or about 0.1 g / cm ^3,
It is needless to say that another embodiment can be realized by setting the uniform density in the range from 0.15 g / cm ³ to 0.15 g / cm ³ . Another variation within the scope of the invention is the use of a first density of soft fluff pulp in combination with a second density of hardwood fluff pulp, in this case the second density
Is preferably higher than the first density.

As used herein, the term "density" refers to the density in the composite structure of low density layer 5 or high density layer 6 and not the actual fiber density.
(Actual fiber density is about 1.5g / cm ^3.) Density of the low density layer 5 should be in the range of about 0.03 to about 0.14 g / cm ^3, when considering the integrity and size The preferred range is about 0.07 to about 0.11 g / cm ³ . High-density layer 6 is about 0.1
4 should be a density of about 0.3 g / cm ^3, in order to generate without extra rigidity desired capillary action is about
A range of 0.16 to 0.22 g / cm ³ is preferred. Such a preferred range of densities is the density measured under a load of 0.2 psi. The important thing to consider in choosing an appropriate range of densities for high and low density fluff is that the pore distribution should be of two different types:
It means that one of them should be formed in each of the layers of each fluff so that the distribution of pores overlaps. The reason for this is that this overlap allows backflow from the high density layer to the low density layer.

The compressed layer 6 may be a layer having a multi-layer structure instead of a single layer structure, and each layer of the layer 6 may increase the density along the width or the length direction of the layer 6 within a specified range. Good or uniform densities are possible. The basis weight of the bottom density layer 5 should be in the range of about 150 to 500 g / m ² in order to make the diaper aesthetically pleasing and comfortable. The basis weight of the dense layer 6 should be in the range of about 150 to 1250 g / m ² .

The high density layer 6 is preferably substantially separated rather than integrally formed with the low density layer 5, which allows better moisture distribution throughout the layer. However, layers 5 and 6 are "substantially separated" even if one layer is formed on top of the other in the same machine, with some mixing at their interfaces. It was formed in. The meaning of this "substantially separated" term is US Patent No.
2,952,260, 2,955,641, 3,017,304, 3,06
Rather than being a substantially single layer having a "skinned" surface as disclosed in 0,936 and 3,694,362, it is merely the formation of two substantially separate layers. is there. Therefore, the compression should be done uniformly through the dense layer 6 and substantially skinning (sk
Care should be taken not to cause inning). In this case, such skinning is that described in the above-mentioned patent or U.S. Pat. No. 4,103,062.
Skinning causes undue stiffness in the fluff, which reduces the absorbent capacity of the bonded (skinned) layer. To avoid skinning, excess water can be removed and both platens maintained at about the same temperature to prevent condensation in the material thickness. The present invention avoids compressing the fluff to the extent that a skin layer is formed, which allows the compressed fluff layer 6 to retain a porosity of at least about 80%, which results in a very large absorption capacity. Occurs.

The compression of the layer 6 takes place in a hot press. Such a press can use, for example, the "Dake Laboratory Press (Model No. 44-148) by Dake of Grand Haven, Mich., Which has a thermal platen that operates under appropriate temperature and pressure conditions. And achieve the desired compression.
Alternatively, as is known in the art, it is preferred to use a thermal calender nip for the compression step.

Ground wood pulp (fluff) is suitable for the present invention,
As another cellulosic fiber, for example, cotton linter can be used. A preferred fluff is Nanfang pine kraft wood pulp (made by sulfate treatment commonly known in the art), bleached,
For example, ITT Rayoneer or International Paper Company
per Company). A suitable hardwood fluff pulp is Southern Hardwood Kraft, available from Weyerhauser as "New Bern 309".

Superabsorbent materials are available from Grai Processing Company (Grai, Muscaten, Iowa).
Water Lock (trademark) J-500 or A-100, which is a product of n Processing Company). Suitable inner liner 2 and outer cover 3 are readily available,
These are well known in the art.

Of course, many changes and modifications can be made to the preferred embodiments described herein without departing from the invention. For example, it is also possible to use other absorbents of lower density as the compressed fluff layer 6, such as (melt-blown polymer fibers mixed with wood pulp and / or staple fibers). There are coformed webs, carded webs, air-formed (stable wood pulp mixture) webs and the like. Furthermore, the absorbent structure described herein has applications for things other than diapers and can be used, for example, as sanitary napkins and other sanitary materials. Therefore, the preferred embodiments described herein are illustrative and not limiting in any way, and the scope of the present invention is limited by the claims including all equivalents.

The advantages gained from the present invention can be fully understood from the following examples and test data.

Example I High density fluff was prepared by heating the fluff at a temperature of 250 ° F and a speed of 30.
It was done by passing it through a high temperature calender nip (steel laminated on hard rubber) at 4.80 cm / min (10 ft / min). The nip pressure was measured at a density of 0.15 after standing overnight.
It was set to a value sufficient to reach g / cm ³ . Alternatively, the fluff can be compacted in a platen press lined with blocks heated to about 250 ° F. for about 5 seconds at a pressure sufficient to achieve the desired fluff density.

The low density fluff was made by passing the fluff through a hot calender nip at a temperature of 250 ° F and a speed of 304.80 cm / min (10 ft / min). The nip pressure was set to a value sufficient to give a measured density of 0.1 g / cm ^{3 after} standing overnight.

In both of the above cases, the fluff was made from southern pine bleached kraft wood pulp and cut to dimensions to meet the weight conditions listed in Table I below. The mixed weights of low and high density fluff are listed in the first column of Table I. The total weight of the sorbent body is maintained at about 37 grams for each diaper, with the exception of diapers with superabsorbents. The diaper in which the superabsorbent is located as shown in FIG.
It has a composite part of gram superabsorbent, which is about 3 grams of particulate superabsorbent (trade name: Water Lock
(A-100, manufactured by Grain Processing Company)
And; about 3 grams of polyolefin; and about 1 gram of porous non-woven wrap. This composite part was made as described in the specification of US Pat. No. 4,381,782. The structure of the diaper is formed by sandwiching the absorbent composite part between the porous non-woven polypropylene liner (23 g / yd ² ) and the polyethylene film outer cover, and sealing the outer circumference of the diaper together with an adhesive. It Five types of diapers corresponding to the descriptions in Table I were constructed by this method. Next, each diaper is made of synthetic urine
It was subjected to a 15 minute vertical wicking test. That is, it was carried out after being in equilibrium for 15 minutes after being contacted with a tank of synthetic urine. The results of this test are shown in Table I and in Figures 10-14.

In this test, a lucite plate (0.9525 cm x 33.02 cm) with multiple impermeable backings adjacent to the surface
(35 × 56 cm) (3/8 ″ × 13 ″ × 14 ″) was placed on a diaper whose weight was previously measured. The diaper should be wrapped symmetrically around the edges of the plate, and the vertical dimension of the diaper should be set. The edges of the waistline of the diaper were placed on the plate with masking tape, and elastic leg bands were used to facilitate this placement. Cut at a few places.

The plate was suspended vertically above the fluid bath in a glass tray. This glass tray has the same longitudinal dimension as the diaper perpendicular to the fluid surface. Then, the fluid was brought into contact with the lower end of the diaper, and the lower end of the diaper was slightly dipped, and this state was maintained for 15 minutes. Then take the diaper out of contact with the fluid and hang it in the same vertical direction,
Equilibrated for 15 minutes. The fluid used in the diapers listed in Table I was synthetic urine, which contained 1% by weight urea, 0.01% by weight Pluronic 10R8 surfactant with a surface tension of about 56 dynes / cm, and 0.04% by weight azide. Made of sodium preservative.

After equilibration, the diaper was removed from the plate, weighed and the amount of fluid uptake recorded. Table I is a summary of these measurements, displaying the average of 7 measurements in each diaper.

After measuring the weight, place the diaper horizontally and 7.62 cm x 38.1 cm
(3 ″ × 5 ″) Placed on the die. This die has a cutting edge in its width direction along with its outer edge and is divided into nine parts, or 4.318 cm (1.7 inches). A 7.62 cm (3 inch) wide absorbent piece was divided into nine parts along the longitudinal axis of the diaper by applying several sharp hits with a wooden mallet. Each absorbent body of the sectioned portion is weighed, dried open and then weighed again,
This (corrected for solids deposited from the fluid)
The amount of fluid absorbed (gram) per gram of fiber basis weight was determined.

In the case of diapers with superabsorbent pouches, the composition of synthetic urine was adjusted to more closely resemble the electrolyte composition of infant urine. That is, the composition of this synthetic urine is: 0.31 grams of CaH ₄ (PO ₄ ) ₂ H ₂ O and 0.68 grams of KH ₂ per liter.
PO ₄ , 0.48 grams MgSO ₄ 7H ₂ O, 1.33 grams K ₂ SO ₄ , 1.2
4 g Na ₃ PO ₄ 12H ₂ O, 4.4 g NaCl, 3.16 g KCl, 0.4 g NaH ₃ , 8.56 urea and 0.1 g Pluronic 10R8, using distilled water as solvent. The components were added in this order to 900 ml of distilled water, each component being dissolved before the next component was added and finally diluted to 1 liter.

The curve shown by the dashed line in FIG. 10 represents the equilibrium capacity of the low density fluff at the hydrostatically indicative tensile force measured in the capillary tension cell. From this figure, it is clear that the fluff reaches its limit capacity only at a short wicking distance (4.5 cm), and a large wicking height (9-18c
m) is much lower than its capacity.

11 to 13 show the fluid suction capacity of the compressed fluff layer for the indicated hydrostatic head. A comparison of the amount of fluid in the low density fluff on the back side of the diaper with the amount of fluid of the same material on the front side at the same hydrostatic head is a measure of the effectiveness of high density fluff for improving the utilization of low density material. Becomes (for example,
In Fig. 13, the rear side 2.8 g / g and the front side when the hydrostatic head is 18 cm
Compare with 0.1g / g).

FIG. 14 shows the effectiveness of the compression layer to transfer fluid to the superabsorbent. The fluid uptake amount in the super absorber is 9 cm of hydrostatic head.
And 12 g / g and 22 g / g at 13.5 cm, respectively. Comparing this result with Fig. 12, we can see the effectiveness of the superabsorbent that diverts the flow of fluid from the fluff portion at the maximum hydraulic head.

What is clear from these results is that the dispersion of the fluid is greatly improved on the rear side of the diaper in the construction with the compressed fluff layer. The contrast with the fluid dispersion on the front side of the diaper without the compressed fluff layer is very clear from each figure. Of course, according to the second and third preferred embodiments,
Better fluid distribution can be obtained on the front side as well as the rear side of the diaper. However, for the following reasons according to the first preferred embodiment for carrying out these tests. That is, for example, when the child is lying on the diaper with the diaper lying on his stomach, such as during sleep, if the excretory liquid is released, the front side of the diaper tends to be completely moist.

Furthermore, these results indicate that fluid dispersion in the low density fluff portion is important. This shows that it is possible to obtain an unexpected cooperative effect in the construction of such a diaper.

In the case of the superabsorbent diaper manufactured according to the fourth embodiment described above, a large amount of fluid flowed from the upper portion of the diaper due to the superabsorbent material. However, the upper edge 8 of the diaper
These parts of the side provide extra absorption capacity when needed.

Example II The inventor has found that similar functions to high density fluff are obtained with hardwood pulp fluff, which is a normal density (0.1 g / cm ³ ) microfiber. This finding has a density of 0.1 g / cm ³
This was done by observing that the distributions of porosity of the hardwood pulp fluff and the softwood fluff of density 0.2 g / cm ³ are strikingly similar. The following tables compare the vertical wicking properties of softwood and hardwood fluff.

The vertical wicking test was somewhat similar to the test performed on all diapers described above. This test uses the same direction and method as described for the diaper, 0.9525 cm.
7.62 cm x 35.56 cm (3 "x 1) placed on a 12.7 cm x 35.56 cm (3/8" x 5 "x 14") Lucite plate
5 ″) piece of absorbent material. A nylon mesh screen was used to support the fluff on a Lucite (acrylic resin) plate. The plate and fluff were then placed on the Instron. Suspended from a weight sensing means, such as a load cell of a tensile tester, and then contacting synthetic urine (in these cases a secondary or salt-containing formulation) with the lower end of the absorbent strip for a period of time. The fluid uptake as a function was recorded at several intervals for a 15 minute continuous test, the uptake being in grams per unit basis weight 1 g / cm ² per unit width (2.54 cm (1 inch)). The vertical wicking capacity was defined as the amount of absorption in the specified units at the end of the 15-minute test, the stated rate is in units per unit width for a time interval of 7-21 seconds. Plot of absorption amount in grammage and time 1/2 It is obtained by et al measured.
The test was repeated 6 times and the results given are the average of these 6 measurements.

The measurement of fluid dispersion in this test is carried out by cutting the sample with a die immediately after the end of the test, the method being the same as described for all diapers. In this case, the portions corresponding to the same height position were put together and the results are shown in Table III.

As estimated from the results in Table II, the vertical wicking capacity of hardwood fluff with a density of 0.1 g / cm ³ closely corresponds to that of softwood fluff with a density of 0.2 g / cm ³ . The initial wicking rate of hardwood fluff is
It is a value between two softwood fluffs. The fluid distribution patterns in Table III also show the similarity between hardwood fluff and softwood fluff with a density of 0.2 g / cm ³ . These results mean that the former has a slightly larger average pore size than the latter.

Therefore, the combination of softwood and hardwood fluff with a density of 0.1 g / cm ³ has similar fluid dispersion properties to the two-layer compressed sandwich structure of softwood fluff described above.

Example III In this example, a double layer of fluff made of softwood fluff covers hardwood fluff. Hardwood fluff is a South American eucalyptus hardwood pulp of ground kraft. The two layers of fluff contained layers of equal weight of softwood and hardwood pulp. Layer 0.
After compressing to a density of 1 g / cm ³ , the vertical wicking properties were as follows:

Comparing the results of the liquid dispersion of the two-layer fluff in Table IV with that of the softwood kraft (Table III), the presence of the eucalyptus layer indicates that the two upper hydrostatic heads (ie,
It has been found that the uptake of fluids (in the range of 13.5 cm and 18 cm) is greatly improved. This is very characteristic since eucalyptus shows only 50% of the two-layer structure.

Example IV 40% by weight superabsorbent (Waterlock J-500, guilein.
A 40 g / m ² web of meltblown polypropylene containing Processing Company was prepared. The superabsorbent is a micromeltblown fiber (surface area of about 1 m ² ) containing sufficient surface active agent (eg, about 0.3-0.5 percent Triton X-102, manufactured by Rohm & Haas Company). / g) to ensure the wettability of the fiber matrix and the composite was compressed to 0.1 g / cm ³ during the manufacturing process.

Using this web, the vertical wicking test described in Example II was performed and the results shown in Table V were obtained. From these results, it is clear that the vertical rise of the fluid is 4.5 cm, where it essentially stops. The reason for this seems to be that the expanding particles were trapped in the pores, which restricted the fluid flow in the web.

This same web was placed in a diaper underneath softwood fluff with a density of 0.2 g / cm ^{3 and} a vertical wicking test (as described in Example I) was conducted on the entire diaper, The effect of the fluff layer as a fluid dispersion member of the absorber was clarified. Table VI shows the fluid dispersion for the entire absorbent composite, the fluff layer itself and the meltblown / superabsorbent web.

Comparing the melt-blown / superabsorbent web vertical dispersion from a diaper (Table VI) with the data in Table V, the action of fluff sucks the fluid higher and improves the dispersion to the superabsorbent ( Values at 9 cm height 11.6 g / g and 1.1 g / g
Compare; also the values at 13.5 cm height are 2.7 g / g and 0.1 g
Compare / g). Here, both tests were similarly performed for 15 minutes. Further, as these tests are continued further, the wicking height of the diaper continues to increase, but the wicking of only the superabsorbent web virtually ceases.

[Brief description of drawings]

FIG. 1 is a perspective view of a first preferred embodiment of the present invention without superabsorbent material. FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. FIG. 3 is a perspective view of a second preferred embodiment of the present invention without superabsorbent material. FIG. 4 is a vertical sectional view taken along line 4-4 of FIG. FIG. 5 is a partial cutaway perspective view of a third preferred embodiment of the present invention having no superabsorbent material. FIG. 6 is a perspective view of a fourth preferred embodiment of the present invention with a portion of superabsorbent material. FIG. 7 is a vertical sectional view taken along line 7-7 of FIG. FIG. 8 is a perspective view of a fifth preferred embodiment of the present invention with a portion of superabsorbent material. FIG. 9 is a vertical sectional view taken along the line 9-9 in FIG. FIG. 10 shows the absorption distribution of the prepared diapers tested in Example 1. FIG. 11 is a diagram showing the absorption distribution of a diaper having a single layer of compressed fluff in addition to the standard fluff portion described in Example 1. FIG. 12 is a diagram showing the absorption distribution of a diaper having two layers of compressed fluff in addition to the standard fluff portion described in Example 1. FIG. 13 is a diagram showing the absorption distribution of a diaper having three layers of compressed fluff in addition to the standard fluff portion described in Example 1. FIG. 14 is a diagram showing the absorbency distribution of the diaper having the two-layer compressed fluff and the superabsorbent material portion described in Example 1. 1 ... diaper, 2 ... liner, 3 ... cover, 4 ...
Liquid absorbing material, 5 ... First layer, 6 ... Second layer, 7 ...
… Target part, 8 …… Top edge, 9… Super absorbent material, 10, 11
...... High-density part.

Claims (18)

[Claims] 1. A liquid permeable liner facing a user's body, a liquid impermeable outer cover, and a liquid absorbent material disposed between the liner and the cover.
The liquid-absorbent material comprises a layer of first cellulose fibers having a first average pore size and a second layer of cellulose fibers having a second average pore size, wherein the second average pore size is the first Less than one mean pore size, the first layer being disposed between the second layer and the fluid permeable liner, the pore size distribution of the first layer and the pores of the second layer. Disposable garments, wherein the maximum size of pores in the second layer is greater than the minimum size of pores in the first layer, due to overlapping size distributions. 2. The garment according to claim 1, wherein the first layer has a density in the range of 0.03 to 0.14 g / cc and the second layer is 0.14 to 0.3 g / cc. Garment characterized by having a density in the range of cc. 3. The garment according to claim 2, wherein the density of the first layer is in the range of 0.07 to 0.11 g / cc. 4. The garment according to claim 2 or 3, wherein the density of the second layer is 0.16 to 0.22.
Clothing characterized by g / cc range. 5. The garment according to any one of claims 1 to 4, wherein each of the layers is mostly composed of soft wood fluff. 6. A garment according to claim 1, wherein the first and second layers have substantially the same density. 7. The garment according to claim 6, wherein the first layer and the second layer are 0.1 to 0.15 g / cc.
Clothing having a density of. 8. The garment according to claim 7, wherein the first layer and the second layer have a density of 0.1 g / cc. 9. The garment according to any one of claims 6 to 8, wherein the first layer comprises a majority of soft wood fluff, and the second layer. Is composed of hard wood fluff for the majority of the clothing. 10. The garment according to claim 9, wherein the first layer is mainly composed of soft wood fluff, and the second layer is composed of hard wood fluff in a majority part. Clothing characterized by that. 11. The garment according to claim 10, wherein the first layer is mainly composed of soft wood fluff and the second layer is mainly composed of hard wood fluff. Clothing characterized by that. 12. A garment as claimed in any one of claims 1 to 11 in which the portion of the superabsorbent material in fluid communication contact with the second layer is provided. Clothing characterized by having. 13. The garment according to claim 12, wherein the superabsorbent material is arranged so as to extend toward a longitudinal end. 14. The garment according to claim 12 or 13, wherein the superabsorbent material is dispersed in a fibrous web. 15. The garment according to claim 14, wherein the web is made of hydrophilic fiber. 16. The garment according to claim 14 or 15, wherein the web is in the form of a bag. 17. The garment according to any one of claims 14 to 16, wherein the web is composed of melt blown fibers mixed with the superabsorbent material. clothing. 18. A garment according to any one of claims 12 to 16, wherein said garment has substantially the same density as said second layer, said layer of superabsorbent material. A garment comprising a third layer disposed below.